Oxygenate separation following oxidative dehydrogenation of a lower alkane

ABSTRACT

A process, a system, and an apparatus are provided for converting a lower alkane to an alkene. Oxygen and the lower alkane are provided to an ODH reactor to convert at least a portion of the lower alkane to an alkene. An ODH stream comprising the alkene, an oxygenate, steam, and a carbon-based oxide is produced. The bulk of the oxygenate is removed from the ODH outlet stream by non-dilutive cooling, with residual oxygenate being removed using dilutive quenching with a carbonate. Subsequently, separation of the carbon-based oxide from the alkene is achieved using a caustic tower, which also produces spent caustic in the form of a carbonate, which is then used as the carbonate for dilutive quenching. Dilutive quenching using a carbonate allows conversion of the oxygenate to an acetate, which can then be used to simplify separation of the oxygenate from water.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Application No. 62/769,205, which was filed on Nov. 19,2018. The contents of U.S. Application No. 62/769,205 are incorporatedby reference in their entirety as part of this application.

TECHNICAL FIELD

The present disclosure relates generally to oxidative dehydrogenation(ODH) of a lower alkane into an alkene. In some examples, the presentdisclosure relates to separation of an ODH product from a processstream.

BACKGROUND

Olefins like ethylene, propylene, and butylene, can be basic buildingblocks for a variety of commercially valuable polymers. Since naturallyoccurring sources of olefins may not exist in commercial quantities,polymer producers may rely on methods for converting the more abundantlower alkanes into olefins. Typically, a polymer producer can utilizesteam cracking to produce alkenes from the lower alkanes. Steam crackingis a highly endothermic process where steam-diluted lower alkanes aresubjected very briefly to a high temperature of at least 800° C. whichrequires a high energy demand. Additionally, steam cracking can causecoke formation in the reactor which can lead to increased maintenancecosts.

Oxidative dehydrogenation (ODH) is an alternative to steam cracking thatcan be exothermic, can have a low energy demand, and can produce littleor no coke. In ODH, a lower alkane is mixed with oxygen in the presenceof a catalyst and optionally an inert diluent at low temperatures suchas, for example 300° C., to produce the corresponding alkene. In someexamples, various other by-products such as, for example, carbonmonoxide, carbon dioxide, and an oxygenate may also be produced in theODH process. The by-products may be subject to further processing priorto being a marketable product or may be disposed of. The additionalprocessing can increase the complexity of a chemical complex and caninclude a high energy demand.

SUMMARY

In one aspect, a method is provided to convert a lower alkane to analkene. More specifically, an input stream comprising oxygen and thelower alkane is provided to an oxidative dehydrogenation (ODH) reactor.At least a portion of the lower alkane is converted to the alkene in theODH reactor and an ODH outlet stream comprising the alkene, anoxygenate, and a carbon-based oxide is produced. The ODH outlet streamis cooled and at least a portion of the oxygenate is condensed. Thealkene is separated from the oxygenate to produce an alkene outletstream and an oxygenate outlet stream. The alkene outlet streamcomprises at least a substantial portion of the alkene and at least asubstantial portion of the carbon-based oxide. The oxygenate outletstream comprises at least a substantial portion of the condensedoxygenate.

In another aspect, an apparatus is provided for oxidativedehydrogenation (ODH) of a lower alkane to an alkene. More specifically,the apparatus comprises an ODH reactor, a means for cooling, and a flashdrum. The ODH reactor comprises an ODH inlet and an ODH outlet. The ODHinlet is suitable for transporting an ODH inlet stream comprising thelower alkane into the ODH reactor. The ODH outlet is suitable fortransporting an ODH outlet stream comprising the alkene, an oxygenate,water in the form of steam, and a carbon-based oxide. The means forcooling is suitable for cooling the ODH outlet stream and condensing atleast a portion of the oxygenate. The flash drum comprises a drum inlet,an oxygenate outlet, and an alkene outlet. The drum inlet is in fluidcommunication with the ODH outlet, to receive the cooled ODH outletstream. The flash drum is suitable for separating the condensedoxygenate from gaseous alkene and gaseous carbon-based oxide. The alkeneoutlet is suitable for transporting an alkene outlet stream comprisingat least a substantial portion of the alkene and at least a substantialportion of the carbon-based oxide. The oxygenate outlet is suitable fortransporting an oxygenate outlet stream comprising at least asubstantial portion of the condensed oxygenate.

In another aspect, a system is provided for oxidative dehydrogenation(ODH) of a lower alkane. More specifically, the system comprises an ODHreactor, a means for cooling, and a flash drum. The ODH reactor isconfigured to receive an input stream comprising oxygen and the loweralkane. The ODH reactor is configured to produce an ODH outlet streamcomprising an alkene, an oxygenate, water in the form of steam, and acarbon-based oxide. The means for cooling is configured to cool the ODHoutlet stream to produce a cooled ODH outlet stream. The flash drum isconfigured to separate the alkene from the oxygenate to produce analkene outlet stream and an oxygenate outlet stream. The alkene outletstream comprises at least a substantial portion of the alkene and atleast a substantial portion of the carbon-based oxide. The oxygenateoutlet stream comprises at least a substantial portion of the condensedoxygenate.

It is understood that the inventions described in this specification arenot limited to the examples summarized in this Summary Various otheraspects are described and exemplified herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the examples, and the manner of attainingthem, will become more apparent and the examples will be betterunderstood by reference to the following description of examples takenin conjunction with the accompanying drawings, wherein:

FIG. 1 is a flow diagram illustrating a non-limiting example of a systemto convert an alkane to an alkene;

FIG. 2 is a flow diagram illustrating a non-limiting example of a systemcomprising a separation tower;

FIG. 3 is a flow diagram illustrating a non-limiting example of a systemcomprising an oxygen remover;

FIG. 4 is a flow diagram illustrating a non-limiting example of a systemcomprising an amine tower; and

FIG. 5 is a flow diagram illustrating a non-limiting example of a systemcomprising a polymerization reactor.

DETAILED DESCRIPTION

The exemplifications set out herein illustrate certain examples, in oneform, and such exemplifications are not to be construed as limiting thescope of the examples in any manner.

Certain exemplary aspects of the present disclosure will now bedescribed to provide an overall understanding of the principles of thestructure, function, manufacture, and use of the systems, apparatus, andmethods disclosed herein. One or more examples of these aspects areillustrated in the accompanying drawings. Those of ordinary skill in theart will understand that the systems and methods specifically describedherein and illustrated in the accompanying drawings are non-limitingexemplary aspects and that the scope of the various examples of thepresent invention is defined solely by the claims. The featuresillustrated or described in connection with one exemplary aspect may becombined with the features of other aspects. Such modifications andvariations are intended to be included within the scope of the presentinvention.

Reference throughout the specification to “various examples,” “someexamples,” “one example,” or “an example”, or the like, means that aparticular feature, structure, or characteristic described in connectionwith the example is included in at least one example. Thus, appearancesof the phrases “in various examples,” “in some examples,” “in oneexample”, or “in an example”, or the like, in places throughout thespecification are not necessarily all referring to the same example.Furthermore, the particular features, structures, or characteristics maybe combined in any suitable manner in one or more examples. Thus, theparticular features, structures, or characteristics illustrated ordescribed in connection with one example may be combined, in whole or inpart, with the features structures, or characteristics of one or moreother examples without limitation. Such modifications and variations areintended to be included within the scope of the present examples.

Other than in the operating examples or where otherwise indicated, allnumbers or expressions referring to quantities of ingredients, reactionconditions, etc. used in the specification and claims are to beunderstood as modified in all instances by the term “about”.Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that can vary depending upon the desired properties,which the present disclosure desires to obtain. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the disclosure are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical values, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between andincluding the recited minimum value of 1 and the recited maximum valueof 10; that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10. Because the disclosednumerical ranges are continuous, they include every value between theminimum and maximum values. Unless expressly indicated otherwise, thevarious numerical ranges specified in this application areapproximations.

The grammatical articles “a”, “an”, and “the”, as used herein, areintended to include “at least one” or “one or more”, unless otherwiseindicated, even if “at least one” or “one or more” is expressly used incertain instances. Thus, the foregoing grammatical articles are usedherein to refer to one or more than one (i.e., to “at least one”) of theparticular identified elements. Further, the use of a singular nounincludes the plural, and the use of a plural noun includes the singular,unless the context of the usage requires otherwise.

As used herein, the term “substantial portion” means at least 50 percentby weight. A substantial portion can be 50% to 100% by weight such as,for example, at least 60% by weight, at least 70% by weight, at least80% by weight, at least 90% by weight, or at least 95% by weight.

As used herein, the term “alkane” refers to an acyclic saturatedhydrocarbon. In various examples, an alkane consists of hydrogen andcarbon atoms arranged in a linear structure in which all of thecarbon-carbon bonds are single bonds. An alkane has the general chemicalformula C_(n)H_(2n+2) and in various examples, for a lower alkane, ‘n’is in a range of 2 to 4. In various examples, an alkane refers to one ormore of ethane, propane, butane, pentane, hexane, octane, decane anddodecane. In various examples, a lower alkane refers to one or more ofethane, propane, and butane.

As used herein, the term “alkene” refers to an unsaturated hydrocarbonthat contains at least one carbon-carbon double bond. In variousexamples, alkene refers to alpha olefins. For example, alkene can referto one or more of ethylene, propylene, 1-butene, butadiene, pentene,pentadiaene hexene, octene, decene, and dodecene.

As used herein, the terms “alpha olefin” or “α-olefin” refer to a familyof organic compounds which are an alkene (also known as olefin) with achemical formula C_(x)H_(2x), distinguished by having a double bond atthe primary or alpha (α) position. In various examples, alpha olefinrefers to one or more of ethylene, propylene, 1-butene, 1-pentene,1-hexene, 1-octene, 1-decene, and 1-dodecene.

As used herein, the term “fixed bed reactor” refers to one or morereactors, in series or parallel, often including a cylindrical tubefilled with catalyst pellets with reactants flowing through the bed andbeing converted into products. The catalyst in the reactor may havemultiple configurations including, for example, one large bed, severalhorizontal beds, several parallel packed tubes, multiple beds in theirown shells, and/or combinations thereof.

As used herein, the term “fluidized bed reactor” refers to one or morereactors, in series or parallel, often including a fluid (e.g., gas orliquid) which can be passed through a solid granular catalyst, which canbe shaped as tiny spheres, at a velocity high enough to suspend thesolid granular catalyst and cause the solid granular catalyst to behavelike a fluid.

As used herein, the term “HDPE” refers to high density polyethylene,which generally has a density of greater or equal to 0.941 g/cm³. HDPEhas a low degree of branching. HDPE can be often produced usingchromium/silica catalysts, Ziegler-Natta catalysts or metallocenecatalysts.

As used herein, the term “LDPE” refers to low density polyethylene,which can be a polyethylene with a high degree of branching with longchains. Often, the density of a LDPE will range from 0.910-0.940 g/cm³.LDPE can be created by free radical polymerization.

As used herein, the term “LLDPE” refers to linear low densitypolyethylene, which can be a polyethylene that can have significantnumbers of short branches resulting from copolymerization of ethylenewith at least one α-olefin comonomer. In some examples, LLDPE has adensity in the range of 0.915-0.925 g/cm³. In some examples, the LLDPEcan be an ethylene hexene copolymer, ethylene octene copolymer, orethylene butene copolymer. The amount of comonomer incorporated can befrom 0.5 mole % to 12 mole % relative to ethylene, in some examples from1.5 mole % to 10 mole %, and in other examples from 2 mole % to 8 mole%.

As used herein, the term “MDPE” refers to medium density polyethylene,which can be a polyethylene with some short and/or long chain branchingand a density in the range of 0.926-0.940 g/cm³. MDPE can be producedusing chromium/silica catalysts, Ziegler-Natta catalysts or metallocenecatalysts.

As used herein, the term “VLDPE” refers to very low densitypolyethylene, which can be a polyethylene with high levels of shortchain branching with a typical density in the range of 0.880-0.915 g/cc.In some examples, VLDPE can be a substantially linear polymer. VLDPE canbe typically produced by copolymerization of ethylene with α-olefins.VLDPE can be produced using metallocene catalysts.

As used herein, the term “gas phase polyethylene process” refers to aprocess where a mixture of ethylene, optional alpha olefin comonomers,and hydrogen can be passed over a catalyst in a fixed or fluidized bedreactor. The ethylene and optional alpha olefins polymerize to formgrains of polyethylene, suspended in the flowing gas, which can pass outof the reactor. In various examples, two or more of the individualreactors are placed in parallel or in series, each of which are underslightly different conditions, so that the properties of differentpolyethylenes from the reactors are present in the resultingpolyethylene blend. In some examples, the catalyst system includes, forexample, chromium catalysts, Ziegler-Natta catalysts, zirconocenecatalysts, and metallocene catalysts and combinations thereof.

As used herein, the term “high pressure polyethylene process” refers toconverting ethylene gas into a white solid by heating it at very highpressures in the presence of minute quantities of oxygen (less than 10ppm oxygen) at 1000 bar-3000 bar and at 80° C.-300° C. In some examples,the high pressure polyethylene process produces LDPE.

As used herein, the term “low pressure polyethylene process” refers topolymerizing ethylene using a catalyst that in some examples includesaluminum at generally lower pressures than the high pressurepolyethylene process. In some examples, the low pressure polyethyleneprocess can be carried out at 10 bar-80 bar and at 70° C.-300° C. Invarious examples, the low pressure polyethylene process provides HDPE.In various examples, an α-olefin comonomer can be included in the lowpressure polyethylene process to provide LLDPE.

As used herein, the term “solution polyethylene process” refers toprocesses that polymerize ethylene and one or more optional α-olefins ina mixture of lower alkane hydrocarbons in the presence of one or morecatalysts. In various examples, two or more of the individual reactorscan be placed in parallel or in series, each of which can be underslightly different conditions, so that the properties of differentpolyethylenes from the reactors are present in the resultingpolyethylene blend. In some examples the catalysts include, but are notlimited to, chromium catalysts, Ziegler-Natta catalysts, zirconocenecatalysts, hafnocene catalysts, phosphinimine catalysts, metallocenecatalysts, and combinations thereof.

As used herein, the term “slurry polyethylene process” refers tosingle-tube loop reactors, double-tube loop reactors or autoclaves(stirred-tank reactors) used to polymerize ethylene and optionalα-olefins in the presence of a catalyst system and a diluent.Non-limiting examples of diluents include isobutane, n-hexane, orn-heptane. In some examples, two or more of the individual reactors areplaced in parallel or in series, each of which can be under slightlydifferent conditions, so that the properties of different polyethylenesfrom the reactors are present in the resulting polyethylene blend. Insome examples, the catalyst system includes, for example, chromiumcatalysts, Ziegler-Natta catalysts, zirconocene catalysts, hafnocenecatalysts, phosphinimine catalysts, metallocene catalysts, andcombinations thereof.

As used herein, the term “long chain branching” refers to a situationwhere during α-olefin polymerization, a vinyl terminated polymer chaincan be incorporated into a growing polymer chain. Long branches oftenhave a length that can be longer than the average critical entanglementdistance of a linear (e.g., no long chain branching) polymer chain. Insome examples, long chain branching effects melt rheological behavior.

As used herein, the term “short chain branching” refers to a copolymerof ethylene with an α-olefin or with branches of less than 40 carbonatoms. In some examples, the α-olefin or branches are present at lessthan 20% by weight of the polyethylene, in some examples less than 15%by weight. In some examples, the presence of short chain branches caninterfere with the formation of the polyethylene crystal structure andcan be observed as a lower density compared with a linear (no shortchain branching) polyethylene of the same molecular weight.

As used herein, the term “monomer” refers to small molecules containingat least one double bond that can react in the presence of a freeradical polymerization initiator to become chemically bonded to othermonomers to form a polymer.

As used herein, the term, “olefinic monomer” includes, withoutlimitation, α-olefins, and in some examples, ethylene, propylene,1-butene, 1-hexene, 1-octene, and combinations thereof.

As used herein, the term “polyolefin” refers to a material, which isprepared by polymerizing a monomer composition containing at least oneolefinic monomer.

As used herein, the term “polyethylene” can include, for example, ahomopolymer of ethylene, a copolymer of ethylene, and an α-olefin.

As used herein, the term “polypropylene” can include a homopolymer ofpropylene such as, for example, isotactic polypropylene and syndiotacticpolypropylene, a copolymer of propylene, and an α-olefin.

As used herein, the term “polymer” refers to macromolecules composed ofrepeating structural units connected by covalent chemical bonds and caninclude, for example, a homopolymer, a random copolymer, a blockcopolymer, and a graft copolymer.

As used herein, the term “thermoplastic” refers to a class of polymersthat can soften or become liquid when heated and can harden when cooled.In some examples, a thermoplastic can be a high-molecular-weight polymerthat can be repeatedly heated and remolded. In various examples, athermoplastic resin can include a polyolefin and an elastomer that hasthermoplastic properties.

As used herein, the terms “thermoplastic elastomers” and “TPE” refer toa class of copolymers or a blend of polymers (in some examples a blendof a thermoplastic and a rubber) which includes materials having boththermoplastic and elastomeric properties.

As used herein, the terms “thermoplastic olefin” or “TPO” refer topolymer/filler blends that contain some fraction of polyethylene,polypropylene, block copolymers of polypropylene, rubber, and areinforcing filler. The fillers can include, for example, talc,fiberglass, carbon fiber, wollastonite, metal oxy sulfate, andcombinations thereof. The rubber can include, for example,ethylene-propylene rubber, EPDM (ethylene-propylene-diene rubber),ethylene-butadiene copolymer, styrene-ethylene-butadiene-styrene blockcopolymers, styrene-butadiene copolymers, ethylene-vinyl acetatecopolymers, ethylene-alkyl (meth)acrylate copolymers, and VLDPE such asthose available under the Flexomer® resin trade name from the DowChemical Co., Midland, Mich.,styrene-ethylene-ethylene-propylene-styrene (SEEPS). These can also beused as the materials to be modified by the interpolymer to tailor theirrheological properties.

Unless otherwise specified, all molecular weight values are determinedusing gel permeation chromatography (GPC). Molecular weights areexpressed as polyethylene equivalents with a relative standard deviationof 2.9% for the number average molecular weight (“Mn”) and 5.0% for theweight average molecular weight (“Mw”). Unless otherwise indicated, themolecular weight values indicated herein are weight average molecularweights (Mw).

Unless otherwise specified, all pressure values are absolute pressurevalues.

Composition of gaseous streams can be described in many ways, as knownto a person skilled in the art. For oxidative dehydrogenation, numerousstreams are described and can be partially describe in terms of thechemical composition. Unless otherwise specified, the chemicalcomposition of a chemical species within streams is measured in terms ofmole percent (mol %) which is calculated by determining the moles of thespecies and dividing by the total number of moles of all species in thestream and multiplying by 100. Converting to mass fraction or masspercent is within the knowledge of the person skilled in the art and canbe performed given sufficient information about the stream with respectto flow rates, temperature, and pressure.

Oxidative dehydration (ODH) can couple the endothermic dehydration of analkane with the strongly exothermic oxidation of hydrogen. For example,ODH of an alkane can comprise contacting an alkane and oxygen in an ODHreactor with an ODH catalyst under reaction conditions (e.g.,temperature, pressure, flow rate, etc.) that can promote oxidation ofthe alkane into the corresponding alkene. The corresponding alkeneincludes hydrocarbons with the same number of carbons as the alkane usedin the ODH reactor, but with the addition of one carbon to carbon doublebond. For example, utilizing ODH, ethane can be converted to ethylene,propane can be converted to propylene, and butane can be converted tobutylene.

Any ODH catalyst known in the art can be suitable for use with thepresent disclosure. For example, an ODH catalyst containing a mixedmetal oxide can be used. Additionally, reaction conditions can becontrolled to adjust the selectively and yield of the ODH reactorproducts. As known in the art, conditions will vary and can be optimizedfor a particular alkane, for a specific catalyst, a select product,and/or a particular inert diluent.

A product of an ODH reaction can be an oxygenate such as, for example,acetic acid, acrylic acid, maleic acid, and maleic anhydride. Theoxygenate can require purification and/or further processing in order togenerate a marketable product. For example, water may have to be removedfrom the oxygenate. Separation of the oxygenate from water can increasethe complexity of a quench tower and/or a separation tower due to thesmall thermal (e.g., boiling point) separation between the oxygenate andthe water. In various examples, a mixture of oxygenate and water can beazeotropic. The separation tower may employ a large column, a highquantity of stages, a high reflux ratio, and a high energy demand toseparate an azeotropic mixture of oxygenate and water.

Thus, a method, a system, and an apparatus are provided which canenhance the purification of the oxygenate and reduce energy requirementsfor the purification. More specifically, a method, a system, and anapparatus are provided for converting a lower alkane to an alkene. Aninput stream comprising oxygen and the lower alkane can be provided toan ODH reactor. At least a portion of the lower alkane can be convertedto the alkene in the ODH reactor and an ODH outlet stream comprising thealkene, an oxygenate, water in the form of steam, and a carbon-basedoxide can be produced. The ODH outlet stream can then be cooled topromote condensation of at least a substantial portion of the oxygenateand a portion of the steam. The ODH outlet stream can then be subjectedto a means for liquid-gas separation to produce a first oxygenate outletstream comprising at least a substantial portion of the condensedoxygenate and water and an alkene outlet stream comprising at least asubstantial portion of the alkane, at least a substantial portion of thecarbon-based oxide, and any remaining oxygenate. Using condensation andliquid-gas separation for removing a substantial portion of theoxygenate from the ODH outlet stream is non-dilutive as no additionalcomponents are added to the ODH outlet stream.

The alkene outlet stream can be provided to a quench tower and remainingoxygenate can be removed from the alkene outlet stream. The quenchtower, as known to a person skilled in the art, includes addition of aquench agent, usually water, and is therefore dilutive as an additionalcomponent is added to the stream. A first quench outlet streamcomprising at least a substantial portion of the alkene and at least asubstantial portion of the carbon-based oxide can be produced in thequench tower. Additionally, a second quench outlet stream comprising atleast a substantial portion of the remaining oxygenate can be producedin the quench tower. The first quench outlet stream can be provided to acaustic wash tower. The first quench outlet stream can be contacted witha hydroxide in the caustic wash tower to form a caustic outlet streamcomprising a carbonate. The caustic outlet stream can be provided to thequench tower. The alkene outlet stream can be contacted with the causticoutlet stream to form an acetate. The second quench outlet stream cancomprise a substantial portion of the acetate.

Referring to FIG. 1, illustrated is a flow diagram of a non-limitingexample of a system 100 to convert an alkane to an alkene. Asillustrated, an ODH reactor 102, a flash tower 103, a quench tower 104,and a caustic wash tower 106 can be in operative communication. Forexample, an ODH outlet 102 b of the ODH reactor 102 can be in fluidcommunication with a flash tower inlet 103 a of flash tower 103 via anODH outlet line 110. Additionally, a flash tower outlet 103 b of flashtower 103 can be in fluid communication with a quench inlet 104 a of thequench tower 104 via alkene outlet line 110 a. Additionally, a quenchoutlet 104 c of the quench tower 104 can be in fluid communication witha wash inlet 106 a of the caustic wash tower 106 via a quench outletline 114. Accordingly, the ODH reactor 102 can be in fluid communicationwith the caustic wash tower 106 via the flash tower 103 and the quenchtower 104.

The ODH reactor 102 can comprise an ODH inlet 102 a which can beconfigured to receive an ODH inlet stream from an ODH inlet line 108 andcan be suitable to transport the ODH inlet stream into the ODH reactor102. The ODH inlet stream can comprise a gaseous mixture of a loweralkane and oxygen. In various examples, the ODH inlet streamadditionally can include at least one of a carbon-based oxide, steam,and an inert diluent. The inert diluent can comprise, for example,nitrogen, carbon dioxide, steam, and methane. In various examples, thecarbon-based oxide can comprise at least one of carbon dioxide andcarbon monoxide. The concentration of the oxygen and the lower alkanewithin the mixture in the ODH inlet stream and the temperature andpressure of the ODH inlet stream can be adjusted such that the mixturecan be outside of the flammability limits of the mixture.

In various examples, there may be multiple ODH inlet lines configured toprovide the ODH inlet stream to the ODH reactor 102. For example, eachcomponent (e.g., lower alkane, oxygen, steam, carbon-based oxide, andinert diluent) may be added directly to the ODH reactor 102, each inseparate inlet lines (not shown). Alternatively, one or more componentsmay be pre-mixed and added in more than one inlet line. In variousexample, components may be mixed together prior to the ODH reactor 102and subsequently introduced into the ODH reactor in a common ODH inlet.In various examples, steam may be added indirectly as water mixed withan additional reactant and the resulting mixture can be preheated beforeentering the ODH reactor 102. When adding steam indirectly as water, thepreheating process can increase the temperature of the mixture so thatthe water can be substantially converted to steam before entering theODH reactor 102.

The ODH reactor 102 can include a catalyst capable of catalyzing the ODHof the reactants within the ODH inlet stream to products such as, forexample, an alkene, a carbon-based oxide, water, and an oxygenate. Thecatalyst may be, for example, a mixed metal oxide catalyst.

The catalyst composition, temperature and pressure of the ODH reactor102, and the composition of the ODH inlet stream can be adjusted inorder to vary the composition of products as known by one of ordinaryskill in the art. For example, the ratio of the lower alkane to oxygencan be outside of the upper flammability limit of the mixture. Invarious examples, the oxygen concentration in the ODH inlet stream canbe in a range of 0.1% to 30% by weight of the ODH inlet stream, and insome examples range from 0.1% to less than 30% by weight, less than 25%by weight, or less than 20% by weight. In various examples, the loweralkane concentration in the ODH inlet stream can range from 0.1% to 50%by weight of the ODH inlet stream, and in some examples range from 0.1%to less than 50% by weight or less than 40% by weight.

In various examples increasing the steam concentration in the ODH inletstream can increase the amount of oxygenate produced relative to thealkene produced in the ODH reactor 102. In various examples, reducingthe steam concentration in the ODH inlet stream can decrease the amountof oxygenate produced relative to the alkene produced in the ODH reactor102. The concentration of steam in the ODH inlet stream can be in arange of 0.1% to 40% by weight of the total ODH inlet stream 108, and insome examples range from 0.1% to less than 40% by weight, or less than25% by weight. In various examples, the concentration of the stream inthe ODH inlet stream can be at least 1% by weight. In various examples,the ODH inlet stream can comprise 20% oxygen by weight, 40% lower alkaneby weight, and the balance being steam, carbon dioxide, and/or an inertdiluent.

In various examples, the ODH process has a selectivity for thecorresponding alkene (e.g., ethylene in the case of ethane ODH) ofgreater than 95% such as, for example, greater than 98%. The gas hourlyspace velocity (GHSV) within the ODH reactor 102 can be from 500 to30000 h⁻¹ and in some examples the GHSV within the ODH reactor 102 canbe greater than 1000 h⁻¹. In various examples, the linear velocitywithin the ODH reactor 102 can be from 10 cm/s to 500 cm/s. In variousexamples, the weight hourly space velocity (WHSV) within the ODH reactorcan be from 2.1 to 25 h⁻¹. In various examples, the space-time yield ofcorresponding alkene (e.g., productivity) in grams (g)/hour per kilogram(kg) of the catalyst can be at least 900 such as, for example, greaterthan 1500, greater than 3000, or greater than 3500, at an ODH reactortemperature of, for example, 350° C. to 400° C. In various examples, theproductivity of the catalyst can increase with increasing temperature inthe ODH reactor 102 until the selectivity of the alkene decreases.

Use of an ODH reactor for performing an ODH reaction consistent with thedisclosure falls within the knowledge of the person skilled in the art.In various examples, the reaction can be conducted at temperatures in arange of 300° C. to 450° C. such as, for example, 300° C. to 425° C., or330° C. to 400° C. In various examples, the reaction can be conducted atpressures in a range of 0.5 pounds per square inch (psi) to 100 psi(3.447 to 689.47 kPa) such as, for example, 15 psi to 50 psi (103.4 to344.73 kPa). In various examples, the lower alkane can have a residencetime in the ODH reactor 102 in a range of 0.002 seconds (s) to 30 s, orfrom 1 s to 10 s.

The products of the ODH reaction can leave the ODH reactor 102 throughthe ODH outlet 102 b in an ODH outlet stream. The ODH outlet 102 b canbe configured to receive the ODH outlet stream and can be suitable totransport the ODH outlet stream 110 out of the ODH reactor 102 and intothe ODH outlet line 110. In various examples, in addition to theproducts, the ODH outlet stream can include unreacted components fromthe ODH inlet stream such as, for example, lower alkane, carbon-basedoxide, oxygen, steam, inert diluent, and combinations thereof. Invarious examples, the temperature of the ODH outlet stream can be in arange of 100° C. to 450° C., such as for example, 300° C. to 425° C.,and in certain examples 330° C. to 400° C.

Any of the known reactor types applicable for the ODH of an alkane maybe used with the present disclosure. For example, a fixed bed reactor, afluidized bed reactor, or combinations thereof can be used for the ODHreactor 102. In a typical fixed bed reactor, reactants are introducedinto the reactor at an inlet and flow past an immobilized catalyst.Products are formed and leave through the outlet of the reactor. Aperson skilled in the art would understand which features are requiredwith respect to shape and dimensions of the reactor, inputs forreactants, outputs for products, temperature and pressure control, andmeans for immobilizing the catalyst.

In a typical fluidized bed reactor, the catalyst bed can be supported bya porous structure or a distributor plate and located near a lower endof the reactor. Reactants flow through the fluidized bed reactor at avelocity sufficient to fluidize the bed (e.g., the catalyst rises andbegins to swirl around in a fluidized manner). The reactants can beconverted to products upon contact with the fluidized catalyst and thereactants are subsequently removed from an upper end of the reactor. Aperson of ordinary skill in the art would understand which features arerequired with respect to shape and dimensions of the reactor, the shapeand size of the distributor plate, the input temperature, the outputtemperature, the reactor temperature and pressure, inputs for reactors,outputs for reactants, and velocities to achieve fluidization.

In various examples, there may be multiple ODH reactors connected inseries or in parallel. Each ODH reactor may be the same or different.For example, each ODH reactor can contain the same or different ODHcatalyst. In various examples, the multiple ODH reactors can each be afixed bed reactor, can each be a fluidized bed reactor, or the multipleODH reactors can be combinations of fixed bed reactors and fluidized bedreactors.

Regardless of the configuration of the ODH reactor 102, the ODH outlet102 b can be in fluid communication with the flash tower inlet 103 a ofthe flash tower 103 via ODH outlet line 110 to direct the ODH outletstream to the flash tower 103. The ODH outlet stream is subjected to acooling means 105 prior to reaching flash tower inlet 103 a or withinflash tower 103. The flash tower outlet 103 b can be in fluidcommunication with the quench inlet 104 a of the quench tower 104 viathe alkene outlet line 110 a to direct the alkene outlet stream to thequench tower 104. The quench inlet 104 a can be configured to receivethe alkene outlet stream from the alkene outlet line 110 a and can besuitable to transport the alkene outlet stream into the quench tower104.

The cooling means 105 can be any means that cools the ODH outlet streamafter it leaves the ODH reactor. This can include using a sufficientlylong ODH outlet line 110 that allows the ODH outlet stream to cool to atemperature where the oxygenate begins to condense before reaching flashtower 103. In some embodiments, the most preferable cooling means 105comprise a heat exchanger, use of which is well known within the art. Insome embodiments, the cooling means 105 are an integral part of theflash tower 103. In some examples, the flash tower may be surrounded bya cooling jacket that cools the ODH outlet stream as it enters flashtower 103. In another example, cooling tubes are arranged within thespace inside flash tower 103. In some embodiments, a heat exchanger incombination with integrated cooling means are used to cool to ODH outletstream.

The cooling means can cool the ODH outlet stream to a temperature ofless than 200° C. such as, for example, less than 100° C., less than 50°C., less than 40° C., and in some examples, the cooling means 105 cancool the ODH outlet stream to a temperature of 20° C. to 80° C. Invarious examples, the cooling means 105 can cool the ODH outlet streamto a temperature which induces condensation of the oxygenate such as,for example, to a temperature less than or equal to the boiling point ofthe oxygenate and/or a temperature that reduces the vapor pressure ofthe oxygenate. The lower the temperature, without going below atemperature that results in freezing of the water or oxygenate, thegreater the degree of condensation, which would be understood by aperson skilled in the art.

Flash tower 103 can comprise a flash tower, or any other means thatprovides for gas-liquid separation. Use of flash towers is well known.At least a substantial portion of the oxygenate and water, in the formof steam, within the ODH outlet stream may be in a liquid state afterbeing subjected to cooling means 105 and may exit flash tower 103through a first oxygenate outlet 103 c, as a first oxygenate outletstream, and into the first oxygenate outlet line 111. In variousexamples, the first oxygenate outlet stream can comprise at least 0.5mol % oxygenate, such as, for example, at least 2.0 mol % oxygenate, atleast 5 mol %, or 0.5 mol % to 15 mol % oxygenate. The first oxygenateoutlet stream can additionally comprise water of from 80 mol % to 99.5mol %.

A portion of the oxygenate and water within the ODH outlet stream,including liquid and gaseous forms, may leave the flash tower 103 aspart of the alkane outlet stream. These portions are referred to asremaining oxygenate and remaining water, respectively.

In various examples, the alkene outlet stream may be subject to a secondcooling means prior to or as an integral part of quench tower 104. Thesecond cooling means can be configured to adjust the temperature of thealkene outlet stream, for example, by cooling to a temperature of lessthan 200° C. such as, for example, less than 100° C., less than 50° C.,less than 40° C., and in some examples, the second cooling means cancool the alkene outlet stream to a temperature of 20° C. to 80° C. Invarious examples, the second cooling means can cool the alkene outletstream to a temperature which induces condensation of the remainingoxygenate such as, for example, a temperature less than or equal to theboiling point of the remaining oxygenate and/or a temperature thatreduces the vapor pressure of the remaining oxygenate. The secondcooling means can use any means known in the art. For example, thesecond cooling means can be a standalone heat exchanger separate from aquench tower. In various examples, the second cooling means can be anintegrated heat exchanger that is part of a quench tower. In furtherexamples, the second cooling means may include a combination ofstandalone heat exchanger and an integrated heat exchanger.

The quench tower 104 can comprise a quench tower, an oxygenate scrubber,the like, or combinations thereof. The quench tower 104 can beconfigured to quench the components in the alkene outlet stream andremove at least a substantial portion of the alkene from the alkeneoutlet stream. In various examples, the quench tower 104 can facilitatethe removal of remaining oxygenate and water from the alkene outletstream. The quench tower 104 can produce a first quench outlet streamcomprising at least a substantial portion of the alkene and at least asubstantial portion of the carbon-based oxide from the alkene outletstream. In various examples, the first quench outlet stream can compriseadditional components from the alkene outlet stream such as, forexample, a portion of the oxygen, a portion of the oxygenate, a portionof the inert diluent, a portion of the steam, and a portion of theunreacted alkane. The first quench outlet stream exits the quench tower104 through the quench outlet 104 c. The quench outlet 104 c can beconfigured to receive the first quench outlet stream and can be suitableto transport the first quench outlet stream out of the quench tower 104into the quench outlet line 114.

The quench tower 104 can produce a second quench outlet streamcomprising at least a substantial portion of any remaining oxygenatepresent in the alkene outlet stream and in some examples, an acetate asdiscussed herein. In various examples, the second quench outlet streamcan comprise additional components from the alkene outlet stream suchas, for example, a substantial portion of the remaining water (e.g.,steam), as well as lower alkane, alkene, oxygen, and carbon-based oxide.The second quench outlet stream can exit the quench tower 104 throughsecond quench outlet 104 b of the quench tower 104. The second quenchoutlet 104 b can be configured to receive the second quench outletstream and can be suitable to transport the second quench outlet streamout of the quench tower 104 into the second quench outlet line 112.

The quench tower 104 also comprises a carbonate inlet 104 d forproviding a quenching agent such as water via quench agent line 118 a,or a carbonate solution via return line 118. Use of quench towers iswell known. A person skilled in the art would understand that quenchingcondenses and dilutes the oxygenate. The result is that second quenchoutlet stream comprises a lower mol % of the oxygenate compared to thefirst oxygenate outlet stream. When using a carbonate solution as thequench agent the effect is more pronounced as a portion of the oxygenateis converted to an acetate, as will be described.

In some examples, the quench agent is provided to the quench tower at atemperature of less than 200° C. such as, for example, less than 100°C., less than 50° C., less than 40° C., and in some examples, the quenchagent is provided to the quench tower at a temperature of 20° C. to 80°C. In various examples, the quench agent can be provided to the quenchto a temperature which induces condensation of the remaining oxygenatesuch as, for example, a temperature less than or equal to the boilingpoint of the remaining oxygenate and/or a temperature that reduces thevapor pressure of the remaining oxygenate.

The quench outlet 104 c can be in fluid communication with the washinlet 106 a of the caustic wash tower 106 via the quench outlet line 114to direct the first quench outlet stream to the caustic wash tower 106.The wash inlet 106 a can be configured to receive the first quenchoutlet stream from the quench outlet line 114 and can be suitable totransport the first quench outlet stream into the caustic wash tower106.

The caustic wash tower 106 can comprise the wash inlet 106 a, a washoutlet 106 c, a caustic inlet 106 d, and a caustic outlet 106 b. Thecaustic inlet 106 d can be configured to receive a hydroxide streamcomprising a hydroxide from a hydroxide line 120 and can be suitable totransport the hydroxide stream into the caustic wash tower 106. Thehydroxide may be, for example, an aqueous solution of at least one ofsodium hydroxide, potassium hydroxide, and ammonia hydroxide. In variousexamples, the aqueous solution comprises at least 0.5 mol % hydroxide,such as, for example, at least 1.0 mol % hydroxide, at least 1.25 mol %,or 0.5 mol % to 1.75 mol % hydroxide.

The caustic wash tower 106 can be configured to contact the hydroxidestream with the first quench outlet stream. In various examples, wherethe carbon-based oxide comprises carbon dioxide, the hydroxide can reactwith carbon dioxide in the first quench outlet stream to form acarbonate. The reaction can remove at least a substantial portion of thecarbon-based oxide (e.g., carbon dioxide) from the first quench outletstream and produce a wash outlet stream and a caustic outlet stream. Thecarbonate may be, for example, at least one of sodium bicarbonate,potassium carbonate, and ammonium bicarbonate. For example, the reactionof sodium hydroxide and carbon dioxide is shown in Scheme 1.

The wash outlet stream can comprise unreacted components from the firstquench outlet stream. The wash outlet 106 c can be configured to receivethe wash outlet stream and can be suitable to transport the wash outletstream out of the caustic wash tower 106 into the wash outlet line 116.

The caustic outlet stream can comprise a substantial portion of thecarbonate and in some examples, at least one of water, hydroxide, andoxygenate. The caustic outlet 106 b can be configured to receive thecaustic outlet stream and can be suitable to transport the causticoutlet stream into the return line 118. The return line 118 can beconfigured to receive the caustic outlet stream and output the causticoutlet stream into a carbonate inlet 104 d of the quench tower 104.

In various examples, the caustic outlet stream can comprise at least 0.5mol % carbonate, such as, for example, at least 2.0 mol % carbonate, atleast 5 mol %, or 0.5 mol % to 15 mol % carbonate. The caustic outletstream can additionally comprise water of from 80 mol % to 99.5 mol %.

The quench tower 104 can be configured to contact the caustic outletstream with the alkene outlet stream. In various examples, the quenchtower 104 can be configured to react the caustic outlet stream with thealkene outlet stream to form an acetate. In various examples, the quenchtower 104 can react the carbonate with the oxygenate, and in someexamples, with water and hydroxide, to form the acetate. The acetate cancomprise at least one of sodium acetate, potassium acetate, and ammoniumacetate. As an example, the reaction of sodium bicarbonate and theoxygenate to form sodium acetate is illustrated by the reaction inScheme 2.

In various examples, the mole ratio of the carbonate in the causticoutlet stream to oxygenate in the alkene outlet stream can be in a rangeof 0.8:1 to 1.2:1 such as for example, 1:1. In various examples, themole ratio of the carbonate in the caustic outlet stream to oxygenate inthe alkene outlet stream can be greater than 1:1 such as, for example,2:1.

In various examples, the quench tower 104 can be configured to maintaina pH in a range of 2 to 12 such as, for example, 4 to 7. In variousexamples, the quench tower 104 can be configured to maintain a pH in arange of a pKa of the oxygenate to a pKa of the carbonate in order tofacilitate the formation of the acetate. In various example, theoxygenate comprises acetic acid having a pKa of 4.7 and sodiumbicarbonate having a pKa of 6.4.

The first quench outlet stream can comprise a substantial portion of thecarbon-based oxide produced in the quench tower 104 and from the alkeneoutlet stream. The second quench outlet stream can comprise theoxygenate, the acetate, and water. Adding the caustic outlet stream tothe quench tower can decrease the amount of oxygenate and increase theamount of acetate in the first quench outlet stream. The decrease inoxygenate in the first quench outlet stream can be a result of theconversion of the oxygenate to the acetate. The conversion of theoxygenate to the acetate can facilitate the removal of the oxygenatefrom the alkene outlet stream and limit the oxygenate from exiting thequench tower 104 in the first quench outlet stream.

In various examples, the second quench outlet stream can comprise atleast 0.1 mol % oxygenate, such as, for example, at least 0.5 mol %oxygenate, at least 1 mol %, or 0.1 mol % to 5 mol % oxygenate. Thesecond quench outlet stream can additionally comprise at least 0.25 mol% acetate, such as, for example, at least 1.75 mol % oxygenate, at least5 mol %, or 0.25 mol % to 15 mol % acetate water of from 80 mol % to99.5 mol %.

In various examples, the oxygenate in the first oxygenate outlet streamand the second quench outlet stream may be subject to furtherprocessing. For example, referring to FIG. 2, the oxygenate can beseparated from the acetate in a separation tower 326. FIG. 2 is a flowdiagram of a non-limiting example of a system 300 comprising theseparation tower 326. As illustrated, the separation tower 326 has aseparation inlet 326 a, a first separation outlet 326 b, and a secondseparation outlet 326 c. The separation inlet 326 a can be configured toreceive the first oxygenate outlet stream from first oxygenate outletline 111 and the second quench outlet stream from the second quenchoutline line 112 and may be suitable to transport at least one of thefirst oxygenate outlet stream and the second quench outlet stream intothe separation tower 326.

The separation tower 326 can separate the oxygenate from the acetateand, in various examples, the separation tower 326 can separate theoxygenate from water. The presence of the acetate in the separationtower 326 can enhance the separation of oxygenate from the water. Forexample, the acetate and oxygenate may disassociate and/or react withwater to form an acetate ion (e.g., CH₃COO⁻) and an acid (e.g., H₃O⁺,Na⁺). Since the acetate and oxygenate can form a common ion, an increasein the concentration of one of the acetate and oxygenate can affect theother. For example, the reactions of sodium acetate (C₂H₃NaO₂), aceticacid (CH₃COOH), bicarbonate ion (HCO₃ ⁻), carbon dioxide (CO₂), andwater (H₂O) is illustrated in Scheme 3.

As illustrated in Scheme 3, sodium acetate can form an acetate ion whichcan affect the equilibrium reaction of acetic acid and water. Forexample, the sodium acetate can cause the equilibrium reaction of aceticacid and water to have a higher preference for the separate species ofacetic acid and water than an acetate ion and an acid relative towithout the presence of acetate.

The separation tower 326 can comprise various equipment known to thoseof ordinary skill in the art. For example, the separation tower 326 cancomprise an extraction tower, a packed column, a sieve-tray column, aspray column, a KARR column, a rotating disc contactor, a stirred cellextractor, a rectification tower, a stripper, and combinations thereof.In various examples, the separation tower 326 can comprise aliquid-liquid extractor. Accordingly, the acetate in the oxygenate inletstream can increase the efficiency of the separation tower 326 and canfacilitate efficient separation of the oxygenate from water.

The separation tower 326 can produce a second separation outlet streamcomprising a substantial portion of the oxygenate, from at least one ofthe first oxygenate outlet stream and the second quench outlet stream.In various examples, the second separation outlet stream can compriseadditional components from at least one of the first oxygenate outletstream and the second quench outlet stream, such as, for example, water.In various examples, the second separation outlet stream can comprise atleast 80 mol % oxygenate such as, for example, at least 90 mol %oxygenate, at least 95 mol % oxygenate, or 80 mol % to 100 mol %oxygenate by weight. The second separation outlet stream can exit theseparation tower 326 through the second separation outlet 326 c of theseparation tower 326. The second separation outlet 326 c can beconfigured to receive the second separation outlet stream and can besuitable to transport the second separation outlet stream out of theseparation tower 326 into the second separation outlet line 328.

The separation tower 326 can produce a first separation outlet streamcomprising a substantial portion of the acetate from the second quenchoutlet stream and in various examples, a substantial portion of thewater from the second quench outlet stream. In various examples, thefirst separation outlet stream can comprise at least 10% acetate byweight such as, for example, at least 30% acetate by weight, at least50% acetate by weight, or 30% to 70% acetate by weight. In variousexamples, the first separation outlet stream can comprise at least 5%water by weight such as, for example, at least 10% water by weight, atleast 25% water by weight, or 15% to 50% water by weight. The firstseparation outlet stream can exit the separation tower 326 through thefirst separation outlet 326 b of the separation tower 326. The firstseparation outlet 326 b can be configured to receive the firstseparation outlet stream and can be suitable to transport the firstseparation outlet stream out of the separation tower 326 into the firstseparation outlet line 330.

The separation tower 326 can be configured with a recycle line 332 influid communication with the first separation outlet line 330 and/orfirst separation outlet 326 b. The recycle line 332 can be configured torecycle a portion of the acetate from the first separation outlet streamto the separation tower 326 via the recycle inlet 326 d. The recycleline 332 can be configured to receive a portion of the first separationoutlet stream and can be suitable to transport a recycle stream to arecycle inlet 326 d of the separation tower 326. The recycle inlet 326 dcan be configured to receive the recycle stream and can be suitable totransport the recycle stream into the separation tower 326. For example,the recycle stream can comprise a portion of the acetate from the firstseparation outlet stream, and in various examples, a portion of thewater from the first separation outlet stream.

The recycle line 332 can be configured to recycle the acetate from thefirst separation tower outlet stream until a select concentration ofacetate is achieved in the separation tower 326. In various examples andreferring to FIGS. 1 and 3, the return line 118 can enable additionalgeneration of acetate in the quench tower 104 which would flow to theseparation tower 326 through the second quench outlet line 112 toincrease the concentration of acetate in the separation tower 316.

In various examples, a supplemental acetate stream can be added to theseparation tower 326. In various examples, the supplemental acetate cancomprise ethyl acetate.

In various examples, an oxygen remover 444 can be disposed at any pointintermediate the ODH reactor 102 and the caustic wash tower 106. FIG. 3is a flow diagram of a non-limiting embodiment of a system 400comprising an oxygen remover 444 when situated intermediate the flashtower 103 and the quench tower 104. As illustrated, the oxygen remover444, comprising a remover inlet 444 a and a remover outlet 444 b, can beprovided in fluid communication with the flash tower 103 (FIG. 1) viaalkene outlet line 110 a and the quench tower 104 via remover outletline 446. The remover inlet 444 a can be configured to receive thealkene outlet stream and can be suitable to transport the alkene outletstream into the oxygen remover 444. The oxygen remover 444 can remove asubstantial portion of the oxygen in the alkene outlet stream andproduce a remover outlet stream comprising the alkene outlet stream withthe substantial portion of the oxygen removed. The oxygen remover 444can be of various designs as known in the art. The remover outlet 444 bcan be configured to receive the remover outlet stream and can besuitable to transport the remover outlet stream out of the oxygenremover 444 into the remover outlet line 446. The quench inlet 104 a ofthe quench tower 104 can be configured to receive the remover outletstream.

In another embodiment, the oxygen remover 444 can be situated downstreamthe ODH reactor 102 and upstream the flash tower 103. In anotherembodiment, the oxygen remover 444 can be situated down stream thequench tower 104 and upstream the caustic tower 106. The oxygen removerprecedes the caustic wash tower 106, or an amine tower (describedbelow), as residual oxygen within the first quench outlet stream mayaffect operability of the caustic wash tower, or amine tower. Minimizingthe level of oxygen within the first alkene outlet stream may also beachieved by altering ODH reaction conditions, as would be apparent to aperson skilled in the art.

Referring to FIG. 4, in various examples, an amine tower 548 can bedisposed intermediate the quench tower 104 and the caustic wash tower106. FIG. 4 is a flow diagram of a non-limiting example of a system 500comprising an amine tower 548. As illustrated, the amine tower 548,comprising an amine tower inlet 548 a and an amine tower outlet 548 b,can be provided in fluid communication with the quench tower 104(FIG. 1) via quench outlet line 114 and the caustic wash tower 106 viaamine tower outlet line 550. The amine tower inlet 548 a can beconfigured to receive the first quench outlet stream and can be suitableto transport the first quench outlet stream into the amine tower 548.The amine tower 548 can remove a substantial portion of carbon dioxidein the quench outlet stream and produce an amine tower outlet streamcomprising the first quench outlet stream with the substantial portionof the carbon dioxide removed. The amine tower 548 can be of variousdesigns as known in the art.

The amine tower outlet 548 b can be configured to receive the aminetower outlet stream and can be suitable to transport the amine toweroutlet stream out of the amine tower 548 into the amine tower outletline 550. The wash inlet 106 a of the caustic wash tower 106 can beconfigured to receive the amine tower outlet stream from the amine toweroutlet line 550.

Having a high efficiency oxygenate removal prior to the amine tower 548can limit, and in some examples prevent, amine degradation to presenceof the oxygenate in the amine tower 548. For example, the oxygenate canform heat stable salts with amine in the amine tower 548 which candegrade the efficiency and shorten the operational life of the aminetower 548.

Referring to FIG. 5, in various examples, a polymerization reactor 652can be in fluid communication with the caustic wash tower 106 via thewash outlet line 116. FIG. 5 is a flow diagram of a non-limiting exampleof a system 600 comprising a polymerization reactor 652. As illustrated,the polymerization reactor 652, comprising a polymerization inlet 652 aand a polymerization outlet 652 b, can be provided in fluidcommunication with the caustic wash tower 106 via the wash outlet line116. The polymerization inlet 652 a can be configured to receive the ODHoutlet stream and can be suitable to transport the ODH outlet streaminto the polymerization reactor 652. The polymerization reactor 652 canproduce a polymer from the alkene and produce a polymerization outletstream comprising the polymer. In various examples, the polymercomprises at least one of polyethylene, polypropylene, and polybutylene.The polymerization reactor 652 can be of various designs as known in theart. The polymerization outlet 652 b can be configured to receive thepolymerization outlet stream and can be suitable to transport thepolymerization outlet stream out of the polymerization reactor 652 intothe polymerization outlet line 654.

Concentrations of the components within the system can be measured anyat point in the process using any means known in the art. For example, adetector such as a gas chromatograph, an infrared spectrometer, and aRaman spectrometer can be disposed downstream or upstream of ODH reactor102, quench tower 104, caustic wash tower 106, separator 238, separationtower 326, oxygen remover 444, amine tower 548, and polymerizationreactor 652.

In various examples, the ODH inlet stream 108 can comprise mixtures thatfall within the flammability limits of the components. For example, themixture may exist in conditions that prevent propagation of an explosiveevent. In these examples, the flammable mixture can be created within amedium where ignition can be immediately quenched. In various examples,oxygen and the lower alkanes can be mixed at a point where they aresurrounded by a flame arresting material. Thus, any ignition can bequenched by the surrounding material. Flame arresting material includes,for example, metallic or ceramic components, such as stainless steelwalls or ceramic supports. In various examples, oxygen and lower alkanescan be mixed at a low temperature, where an ignition event may not leadto an explosion, then the mixture can be introduced into the ODH reactorbefore increasing the temperature. Therefore, the flammable conditionsmay not exist until the mixture can be surrounded by the flame arrestingmaterial inside of the reactor.

In various examples, the olefins produced using an ODH reactor, or anyof the processes or complexes described herein, can be used to makevarious olefin derivatives utilizing a polymerization reactor. Olefinderivatives include, but are not limited to, polyethylene,polypropylene, ethylene oxide, propylene oxide, polyethylene oxide,polypropylene oxide, vinyl acetate, vinyl chloride, acrylic esters(e.g., methyl methacrylate), thermoplastic elastomers, thermoplasticolefins, blends thereof, and combinations thereof.

In various examples, ethylene and optionally α-olefins can be producedin an ODH reactor, or any of the processes or complexes describedherein, and are used to make polyethylene utilizing a polymerizationreactor. The polyethylene made from the ethylene and optional α-olefinsdescribed herein can include homopolymers of ethylene, copolymers ofethylene and α-olefins, resulting in HDPE, MDPE, LDPE, LLDPE and VLDPE.

The polyethylene produced using the ethylene and optional α-olefinsdescribed herein can be produced using any suitable polymerizationprocess and equipment. Suitable ethylene polymerization processesinclude, but are not limited to gas phase polyethylene processes, highpressure polyethylene processes, low pressure polyethylene processes,solution polyethylene processes, slurry polyethylene processes andsuitable combinations of the above arranged either in parallel or inseries.

A process for converting a lower alkane to an alkene according to thepresent disclosure can include providing an input stream comprisingoxygen and the lower alkane to an ODH reactor 102. In various examples,providing the input stream to an ODH includes providing oxygen and thelower alkane via separate streams. At least a portion of the loweralkane can be converted to the alkene in the ODH reactor 102. In variousexamples, the alkane can comprise ethane and the alkene comprisesethylene. In various examples, the alkane can comprise propane and thealkene comprises propylene. In various examples, the alkane comprisesbutane and the alkene can comprise butylene. An ODH outlet streamcomprising the alkene, water in the form of steam, an oxygenate, and acarbon-based oxide may be produced. In various examples, the ODH outletstream can comprise at least one of an unreacted alkane and oxygen.

The ODH outlet stream is cooled to allow condensation of a portion ofthe oxygenate and a portion of the steam. The cooled ODH outlet streamis provided to a flash tower 103, or other means for gas-liquidseparation, and at least a substantial portion of the condensedoxygenate and at least a substantial portion of the condensed steam areremoved from the ODH outlet stream to produce an alkene outlet streamcomprising at least a substantial portion of the alkene and at least asubstantial portion of the carbon-based oxide and a first oxygenateoutlet stream comprising at least a substantial portion of the condensedoxygenate and at least a substantial portion of the condensed steam. Invarious examples, the alkene outlet stream can comprise at least one ofoxygenate, steam, unreacted alkane, and oxygen. Oxygenate and steampresent in the alkene outlet stream, referred to as remaining oxygenateand remaining steam, comprise the portions of the oxygenate and steamwithin the ODH outlet stream that fail to condense during cooling, orare carried by the gaseous alkene and gaseous carbon-based oxide as thealkene outlet stream exits the flash tower 103.

The alkene outlet stream can be provided to a quench tower 104 and theremaining oxygenate and the remaining steam can be removed from thealkene outlet stream in the quench tower 104 to produce a first quenchoutlet stream comprising at least a substantial portion of the alkeneand at least a substantial portion of the carbon-based oxide.Additionally, the quench tower 104 can produce a second quench outletstream comprising at least a substantial portion of the remainingoxygenate and at least a portion of the remaining steam. Quench towerstypically involve the quenching of a gaseous stream with water, or otherquench agent, to promote condensation of components within the gaseousstream. The condensed components along with the quench agent fall to thebottom of the tower where they can be removed. The gaseous componentsrise and can be removed from a location near the top end of the quenchtower. The temperature of the quench agent is ideally below that of thecondensation point of the component that is targeted for removal. Foroxygenates, such as acetic acid, the temperature of the quench agent is,for example, between 20° C. and 100° C.

In various examples, at least one of the ODH outlet stream and thealkene outlet stream can be provided to an oxygen remover 444 prior tothe quench tower 104. Oxygen can be removed from at least one of the ODHoutlet stream and the alkene outlet stream in the oxygen remover 444 andto reduce the levels of oxygen within at least one of the ODH outletstream and the alkene outlet stream to from 0 to 5 parts per million(ppm)

The first quench outlet stream can be provided to a caustic wash tower106. The quench outlet stream can be contacted with a hydroxide to forma caustic outlet stream comprising a carbonate. In various examples, thefirst quench outlet stream is contacted with the hydroxide in thecaustic wash tower 106.

In various examples, the first quench outlet stream can be provided toan amine wash tower 548 prior to the caustic waste tower 106. Asubstantial portion of the carbon-based oxide can be removed from thefirst quench outlet stream. The first quench outlet stream with thesubstantial portion of the carbon-based oxide removed can be provided tothe caustic waste tower 106. Use of amines such as diethanolamine,monoethanolamine, methyldiethanolamine, is well known for treating gasesto remove carbon-based oxides.

The caustic outlet stream can be provided the quench tower 104 where itacts as a quench agent, and the alkene outlet stream can be contactedwith the caustic outlet stream to form an acetate. In various examples,the alkene outlet stream is contacted with the caustic outlet stream inthe quench tower 104. The second quench outlet stream outlet stream cancomprise a substantial portion of the acetate. In various examples, thepH of the quench tower 104 can be maintained in a range of 2 to 12 suchas, for example 4 to 7. In various examples, the pH of the quench tower104 can be maintained in a range of a pKa of the oxygenate to a pKa ofthe carbonate.

In various examples, the second quench outlet stream can be provided toa separation tower 326. The oxygenate can be separated from the acetatewithin the second quench outlet stream. A second oxygenate outlet streamcomprising a substantial portion of the oxygenate from the second quenchoutlet stream can be produced. An extraction outlet stream comprising asubstantial portion of the acetate from the oxygenate stream can beproduced. In various examples, a portion of the acetate from theextraction outlet stream can be recycled to the separation tower 326. Invarious examples, a supplemental acetate can be provided to theseparation tower 326 such as, for example, ethyl acetate. In variousexamples, the first oxygenate outlet stream can be provided to theseparation tower 326.

In various examples, olefin derivatives can be produced from the alkene.

The present disclosure can provide an alternative use for the causticwaste stream which limits, and in some examples, can eliminate a need todispose of the caustic waste stream. Additionally, the reuse of thecaustic waste stream can provide a useful product of acetate which canaid in oxygenate separation from the quench outlet stream andpurification of oxygenate in the separation tower. The efficient removalof the oxygenate from the quench outlet stream can length theoperational light of downstream equipment such as protecting the aminetower against fouling and amine solution degradation. Moreover, theacetate can be sold. Furthermore, the efficient purification of theoxygenate can create a marketable product such as, for example, glacialacetic acid.

EXAMPLES

Computational modeling of a liquid-liquid separation vessel usingequations from Scheme 3 using ASPEN Plus® version 8.6 chemical processsimulation software, commercially available from Aspen Technology, Inc.Bedford, Mass., was used to demonstrate the effect of altering thecomposition of the feed, as mass fraction, to the separation tower, thefeed representing the second quench outlet stream, on the composition ofthe second oxygenate outlet stream and the composition of the extractionoutlet stream. The feed components chosen are typical for an ODH processof ethane, and include water and acetic acid, with trace amounts (notshown) of ethane, ethylene, carbon dioxide. Use of acetate in the quenchtower results in sodium acetate contributing to the feed composition.

Example 1

Example 1 represents a feed composition that corresponds to a secondquench outlet stream where the ODH outlet stream was not cooled orsubjected to non-dilutive separation prior to quenching in the presenceof sodium acetate. The feed was modeled at a total mass flow rate of6980 kg/hr and at a pressure of 185.7 kPa gauge.

Example 2

Example 2 represents a feed composition that corresponds to a secondquench outlet stream where the ODH outlet stream was not cooled orsubjected to non-dilutive separation prior to quenching in the presenceof sodium acetate. The feed was modeled at a total mass flow rate of55891 kg/hr and at a pressure of 465 kPa gauge.

Example 3

Example 3 represents a feed composition that corresponds to a secondquench outlet stream where the ODH outlet stream was cooled andsubjected to non-dilutive separation prior to quenching in the presenceof sodium acetate. The feed was modeled at a total mass flow rate of11259 kg/hr and at a pressure of 450 kPa gauge.

Example 4

Example 4 represents a feed composition that corresponds to a secondquench outlet stream where the ODH outlet stream was cooled andsubjected to non-dilutive separation prior to quenching in the presenceof sodium acetate. The feed was modeled at a total mass flow rate of9259 kg/hr and at a pressure of 450 kPa gauge.

TABLE 1 Feed Extraction Outlet Stream Second oxygenate outlet streamExample 1 2 3 4 1 2 3 4 1 2 3 4 Mass CH₃OOH 0.219 0.024 0.144 0.1750.013 0.000 0.070 0.016 0.942 0.954 0.855 0.923 Na⁺ 0.153 0.228 0.1450.176 0.196 0.240 0.160 0.213 0.000 0.000 0.000 0.000 CH₃COO⁻ 0.3920.586 0.372 0.453 0.504 0.616 0.411 0.548 0.000 0.000 0.001 0.000 H₂O0.235 0.162 0.338 0.196 0.235 0.144 0.359 0.222 0.052 0.046 0.144 0.366

As shown in Table 1, the separation tower, as aided by the sodiumacetate, produced the second oxygenate outlet stream comprising at least85% by weight of acetic acid. The separation tower produced anextraction outlet stream comprising at least 99% of the sodium acetate.The sodium acetate can be recycled into the separation tower and/or canbe a commercially marketable product. Additionally, the acetic acid inthe second separation outlet can be a commercially marketable product.

The feed streams in the examples take into account the effect of coolingprior to the quench tower. One skilled in the art would recognize thatwhen the ODH outlet stream is not cooled prior to quenching that alarger quantity of water would be required to quench the steam andacetic acid present in the ODH outlet stream. This explains why inexample 2 a feed composition lower in acetic acid than examples 3 and 4was chosen, despite the fact that in examples 3 and 4 a substantialportion of the acetic acid was removed prior to the quench tower. Asmaller quantity of water was required for quenching in examples 3 and 4resulting in a higher mass fraction for those samples.

The examples demonstrate that acetic acid produced in an ODH process canbe isolated in a more concentrated from using non-dilutive separation,and that the remainder can be captured as a more dilute solution. Thedilute solution can be treated to increase the concentration to amarketable level, and this treatment is simplified by adding spentcaustic in the form of a carbonate to the quenching step.

One skilled in the art will recognize that the herein describedcomponents, devices, operations/actions, and objects, and the discussionaccompanying them are used as examples for the sake of conceptualclarity and that various configuration modifications are contemplated.Consequently, as used herein, the specific examples/embodiments setforth and the accompanying discussion are intended to be representativeof their more general classes. In general, use of any specific exemplaris intended to be representative of its class, and the non-inclusion ofspecific components, devices, operations/actions, and objects should notbe taken limiting.

While the present disclosure provides descriptions of various specificaspects for the purpose of illustrating various aspects of the presentdisclosure and/or its potential applications, it is understood thatvariations and modifications will occur to those skilled in the art.Accordingly, the invention or inventions described herein should beunderstood to be at least as broad as they are claimed, and not as morenarrowly defined by particular illustrative aspects provided herein.

1. A method for converting a lower alkane to an alkene comprising:providing oxygen and the lower alkane to an oxidative dehydrogenation(ODH) reactor; converting at least a portion of the lower alkane to thealkene in the ODH reactor and producing an ODH outlet stream comprisingthe alkene, an oxygenate, and a carbon-based oxide; cooling the ODHoutlet stream and condensing at least a portion of the oxygenate;separating the alkene and the carbon-based oxide from condensedoxygenate to produce an alkene outlet stream comprising at least asubstantial portion of the alkene and at least a substantial portion ofthe carbon-based oxide and a first oxygenate outlet stream comprising atleast a substantial portion of condensed oxygenate.
 2. The method ofclaim 1, wherein the ODH outlet stream comprises from 0.1 mol % to 20mol % of the oxygenate.
 3. The method of claim 1, wherein the ODH outletstream is cooled using a heat exchanger.
 4. The method of claim 1,wherein the ODH outlet stream is cooled to a temperature below theboiling point of the oxygenate.
 5. The method of claim 1, wherein theoxygenate is acetic acid and the ODH outlet stream is cooled to atemperature from 20° C. to 120° C.
 6. The method of claim 1, whereinseparating the alkene from the condensed oxygenate is achieved using aflash drum.
 7. The method of claim 1, wherein the oxygenate in the firstoxygenate outlet stream comprises from 0.5 mol % to 15 mol %.
 8. Themethod of claim 1, further comprising: providing the alkene outletstream to a quench tower; and removing at least a portion of remainingoxygenate from the alkene outlet stream in the quench tower to produce afirst quench outlet stream comprising at least a substantial portion ofthe alkene from the alkene outlet stream and at least a substantialportion of the carbon-based oxide from the alkene outlet stream, and asecond quench outlet stream comprising at least a substantial portion ofthe remaining oxygenate.
 9. The method of claim 8, further comprising:providing the first quench outlet stream to a caustic wash tower;contacting the first quench outlet stream with a hydroxide in thecaustic wash tower to form a caustic outlet stream comprising acarbonate; providing the caustic outlet stream to the quench tower; andcontacting the alkene outlet stream with the caustic outlet stream toform an acetate, wherein the second quench outlet stream comprises asubstantial portion of the acetate.
 10. The method of claim 9, whereinthe carbonate comprises at least one of sodium bicarbonate, potassiumcarbonate, or ammonium bicarbonate.
 11. The method of claim 9, whereinthe hydroxide comprises at least one of sodium hydroxide, potassiumhydroxide, or ammonium hydroxide.
 12. The method of claim 9, wherein theacetate comprises at least one of sodium acetate, potassium acetate, orammonium acetate.
 13. The method of claim 9, wherein the carbon-basedoxide comprises carbon dioxide and further comprising providing thefirst quench outlet stream to an amine wash tower and removing asubstantial portion of the carbon dioxide from the first quench outletstream prior to providing the first quench outlet stream to the causticwash tower.
 14. The method of claim 9, further comprising maintainingthe pH of the quench tower in a range of a pKa of the oxygenate to a pKaof the carbonate.
 15. The method of claim 9, further comprisingmaintaining the pH of the quench tower in a range of 2 to
 12. 16. Themethod of claim 9 further comprising: providing the second quench outletstream to an extraction tower; and separating the oxygenate from theacetate within the second quench outlet stream to produce a secondoxygenate outlet stream comprising a substantial portion of theoxygenate from the second quench outlet stream and an extraction outletstream comprising a substantial portion of the acetate from the secondquench outlet stream.
 17. The method of claim 16, further comprisingrecycling a portion of the acetate from the extraction outlet stream tothe extraction tower.
 18. The method of claim 16 further comprisingproviding the first oxygenate outlet stream comprising a substantialportion of the oxygenate from the ODH outlet stream to the extractiontower.
 19. The method of claim 18, wherein the oxygenate in the secondoxygenate outlet stream comprises from 80 mol % to 98 mol %.
 20. Themethod of claim 1, wherein the ODH outlet stream further comprises atleast one of water, an unreacted alkane, or oxygen.
 21. The method ofclaim 20, further comprising providing the ODH outlet stream to anoxygen remover and removing oxygen from the ODH outlet stream in theoxygen remover.
 22. The method of claim 1, wherein the carbon-basedoxide comprises at least one of carbon monoxide or carbon dioxide. 23.The method of claim 1, wherein the oxygenate comprises at least one ofacetic acid, acrylic acid, maleic acid, or maleic anhydride.
 24. Themethod of claim 1, wherein the lower alkane comprises ethane and thealkene comprises ethylene.
 25. The method of claim 1, wherein the loweralkane comprises propane and the alkene comprises propylene.
 26. Themethod of claim 1, wherein the alkene is used to make an olefinderivative.
 27. The method of claim 26, wherein the olefin derivativecomprises at least one of a polyethylene, a polypropylene, an ethyleneoxide, a propylene oxide, a polyethylene oxide, a polypropylene oxide, athermoplastic elastomer, or a thermoplastic olefin.
 28. The method ofclaim 27, wherein the olefin derivative comprises a polyethyleneselected from at least one of a homopolymer of ethylene, a copolymer ofethylene and an α-olefin, a high density polyethylene (HDPE), a mediumdensity polyethylene (MDPE), a low density polyethylene (LDPE), a linearlow density polyethylene (LLDPE), and a very low density polyethylene(VLDPE). 29-69. (canceled)